Vehicles typically include defoggers to remove fog and frost from vehicle surfaces such as windows and mirrors. A defogger system for a windshield typically directs warm air from the vehicle's heating, ventilating, and air conditioning system (HVAC) onto the windshield to remove fog or melt frost. Other vehicle surfaces, such as rear windows and side mirrors, are typically located in positions in which the use of the HVAC system is not feasible. Accordingly, defogger systems for surfaces such as rear windows and side mirrors typically include electrically resistive heating elements mounted to the surfaces to remove fog or melt frost.
A typical defogger system includes a button or other input device located within the vehicle's passenger compartment. The defogger system is activated only after a driver or passenger of the vehicle depresses the button. The typical defogger system includes a timer that automatically deactivates the defogger system after a predetermined amount of time has elapsed since the button was depressed.